Interpretive Summary: Lactococcus garvieae infection in cultured Nile tilapia, Oreochromis niloticus, (Linnaeus) and pintado, Pseudoplathystoma corruscans, (Spix and Agassiz) from Brazil is reported. The commercial bacterial identification system, Biolog Microlog®, confirmed the identity of L. garvieae. Infectivity trials conducted in Nile tilapia using Brazilian Nile tilapia L. garvieae isolates resulted in a lethal dose (LD50) of 1.4 x 105 colony forming units (CFU)/fish. This is the first evidence of the presence of this pathogen from Brazilian fish. In addition, this is the first report of L. garvieae infection in either Nile tilapia or pintado. Collectively, this evidence expands the geographical range of fish hosts, number of fish hosts harboring L. garvieae and carbon source utilization by L. garvieae fish isolates. Furthermore, the Biolog system may be an alternative technique to PCR for the identification of L.garvieae and discrimination between closely related bacterial species.

Technical Abstract:
Lactococcus garvieae infection in cultured Nile tilapia, Oreochromis niloticus, (Linnaeus) and pintado, Pseudoplathystoma corruscans, (Spix and Agassiz) from Brazil is reported. The commercial bacterial identification system, Biolog Microlog®, confirmed the identity of L. garvieae. Infectivity trials conducted in Nile tilapia using Brazilian Nile tilapia L. garvieae isolates resulted in a lethal dose (LD50) of 1.4 x 105 colony forming units (CFU)/fish. This is the first evidence of the presence of this pathogen from Brazilian fish. In addition, this is the first report of L. garvieae infection in either Nile tilapia or pintado. Collectively, this evidence expands the geographical range of fish hosts, number of fish hosts harboring L. garvieae and carbon source utilization by L. garvieae fish isolates. Furthermore, the Biolog system may be an alternative technique to PCR for the identification of L.garvieae and discrimination between closely related bacterial species.